Wednesday, March 23, 2011

How does yeast react with different mixtures of neutral, basic, and acidic substances?My hypothesis was "If we test yeast's reaction with different mixtures, then the basic one will react the most."

Here is my data:

Mixture

Highest Pressure

Acidic

122.13 kPa

Neutral

117.81 kPa

Basic

128.32 kPa

To conduct this experiment, you will need the following:

Computer

Vernier computer interface

Vernier Gas pressure sensor

1-hole stopper assembly

10 mL graduated cylinder

3% hydrogen peroxide

yeast suspension

3 test tubes

test tube rack

dropper

acidic mixture (diet soft drink)

neutral mixture (skim milk)

basic mixture (stomach antacid)

This is what happened inside the test tubes:

The yeast reacted with the diet soda, the skim milk, and the stomach antacid inside the test tubes. Have you ever watched bread rise? The rising bread is caused by the yeast. So this rising process happens when yeast is introduced to certain substances. If the reaction happens in an enclosed environment or container, the pressure will build because the gas from the rising elements is trying to rise, but is getting trapped.

Questions:

1. In which mixture was the yeast activity greatest? In the stomach antacid (basic) mixture, it was the most pressure (128.32 kPa).

2. In which mixture was the yeast activity least? In the skim milk (neutral) mixture, it was the least pressure (117.81 kPa).

3. What can you conclude from the results of your experiment? I can conclude that basic substances react more with yeast, while neutral and acidic mixtures do not.

Thursday, March 17, 2011

For our Pop Rocks Lab, I predicted that the balloon would fill up to a descent size, but not very big. For the baking soda and vinegar lab, I predicted that the balloon would fill up really big. My hypothesis was "If we fill a soda bottle with soda and pop rocks, and a soda bottle with vinegar and baking soda, both with balloons on the opening, the vinegar and baking soda balloon would fill up more than the soda and pop rocks balloon."

It turns out I was correct. After shaking the soda and pop rocks multiple times, it still could not measure up to the size of the vinegar and baking soda balloon.

Some things that went wrong or not as planned were the pop rocks, the size of the balloons, the flexibility of the balloons, and the different types of soda each group used. The pop rocks' instructions were to "fill the balloon with one package of pop rocks". The balloons we used were entirely too small to fit an entire package of pop rocks, so that probably skewed the results. The balloons were not flexible at all, the would stretch, but were even hard for me to blow up! My group used Original Coca Cola soda, while others used everything from Coke Zero to Sprite. That could have differed the results between groups.

Our groups balloons looked somewhat like this:

Pop Rocks and Soda: Long with a round bulb at the bottom (after being shaken)

Vinegar and Baking Soda: Filled up until the top, were it was almost like a small tube.

Tuesday, March 15, 2011

How does temperature affect the rate of chemical reactions? By speeding up or slowing down the process, of course! "If we change the temperature of the water that the alka-seltzer tablet is introduced to, then it will react faster in cold water." That was my hypothesis. It turns out I was utterly wrong. The fastest time was for the hot water, dissolving completely at 23 seconds.

For the Hot Water experiment, you will need to first fill your beaker with 266 mL of water. Place the thermometer inside the beaker on the hot plate. Heat it on high until it reaches 50 degrees celsius. Next, use the thermometer to take the temperature and record in you notes. (Be ready with start and stop time!) When the water has reached 50 degrees celsius, remove 1 alka-seltzer tablet from its package and carefully drop it into the water. Measure the time it take to fully dissolve in the water. Record the time.

For the Room Temperature experiment, you will need to first will your beaker with 266 mL of room temperature water. Next, place the thermometer inside the beaker to take the temperature after 1 minute and record. Finally, drop 1 alka-seltzer tablet into the water and record the time.

For the Cold Water experiment, you must first fill your beaker to 133 mL of water. Then add a few ice cubes to get it around the 266 mL mark. Stir the ice water for about 60 seconds so the temperature will even out. Place the thermometer in the beaker and record the temperature. Finally, drop 1 alka-seltzer tablet into the water and record the time.

Friday, March 11, 2011

1. Starting materials in a chemical reaction are called: Reactants2. The ending materials in a chemical reaction are called: Products3. The arrow indicates a Chemical change has taken place.4. All reactions have one thing in common: there is a Rearrangement of chemical bonds5. Chemical reactions always involve Breaking old bonds, Forming new bonds, or both.6. In all reactions we still have all of the Atoms at the end that we had at the start.7. In every reaction, there can never be Missing atomsor new atoms.8. Chemical reactions only Rearrange the bonds in the atoms that are already there. 9. Let’s represent a reaction on paper. For example, hydrogen gas (H2) reacts with oxygen gas (O2) to form water(H2O):H2 + O2H2O If we use only the atoms shown, we’d have 4 atoms of H and 3 atoms of O as reactants. This wouldmake 2 molecule of H2O, but we’d have 1 atom of O leftover. However, this reaction only makes H2O. 10. So to make H2O from oxygen gas and hydrogen gas, the balanced equation would be:2 H2 + 2 O2 ----> H2O Which is the same as:

# of atoms in Reactants

Element

# of atoms in Product

2

H

2

2

O

1

11. This idea is called the Law of Conversion of Mass.12. There must be the same atoms and the same number of mass before the reaction (in the reactants) and after the reaction (in the products).13. What is the balanced equation for this reaction?2 Cu + 1 O2 ---> CuO14. In the unbalanced equation there are:Reactants ProductsCu atoms : 1Cu atoms: 1O atom: 2O atom: 115. To balance this equation, we have to add 1 Cu molecules to the products, because this reaction doesn’t make lone O atoms.16. When we added a molecule of CuO, now the number of O atoms is balanced but the number of Cu atoms don’t match. Now we have to add more Cu atoms to the reactants.17. The balanced equation for this reaction is 2 Cu + 1 O2 ---> CuOThis is the same thing as saying:ReactantsProducts# Cu atoms 2= # Cu atoms 2# O atoms 2=# O atoms 218. What is the balanced equation for this reaction? (Use the table to keep track of the atoms on each side.)1 CH4+ 2 O2 ---> 2 H2O + 1 CO2

# of atoms in Reactants

Element

# of atoms in Products

1

C

1

4

H

2

2

O

3

19. What is the balanced equation for this reaction? (Use the table to keep track of the atoms on each side.) 1 N2 + 3 H2 ---> 2 NH3

# of atoms in Reactants

Element

# of atoms in Products

2

N

1

2

H

3

20. What is the balanced equation for this reaction? (Use the table to keep track of the atoms on each side.) 2 KClO3 ---> 2 KCl + 3 O2

# of atoms in Reactants

Element

# of atoms in Products

1

K

1

1

Cl

1

3

O

2

21. What is the balanced equation for this reaction? (Use the table to keep track of the atoms on each side.) 4 Al + 3 O2 ---> 2 Al2O3

# of atoms in Reactants

Element

# of atoms in Products

1

Al

2

2

O

3

Summary1. Chemical reactions always involve Breaking old bonds, Forming new bonds, or both.2. The Law of Conservation of Mass says that the same atoms must be the same atoms and the same number of mass before the reaction (in the reactants) and after the reaction (in the products).3. To balance a chemical equation, you change the number in front of each substance until there are the same number of each type of atoms in both reactants and products.